Non-aqueous secondary batteries typified by lithium-ion secondary batteries are characterized by their high energy density; and thus have been widely used as power sources for portable devices such as portable phones and notebook personal computers. There is a trend toward a further increase in the capacity of lithium-ion secondary batteries as portable devices have become more sophisticated. For this reason, research and development aimed at further improving the energy density have been conducted.
On the other hand, the use of non-aqueous secondary batteries as power sources for products other than portable devices has began recently with improvements in their performance. For example, non-aqueous secondary batteries have been started to be used as power sources for automobiles, motorcycles and mobile units such as robots. To use non-aqueous secondary batteries as power sources for automobiles, motorcycles, and mobile units such as robots, their capacities need to be increased further.
One of the ways to increase the capacity of a non-aqueous secondary battery is to increase the thickness of an electrode mixture layer. However, an increase in the thickness of the electrode mixture layer may result in a decline in the capacity at the time of high-power charging/discharging. One of the causes of this decline is considered to be that the amount of active materials that become distant from the current collector increases as the thickness of the electrode mixture layer increases, thereby causing a decline in the conductivity inside the electrode. As a way to improve the conductivity inside the electrode, for example, Patent Document 1 proposes to include an electron conductive polymer in a positive electrode mixture layer.
Further, as other way to increase the capacity of a non-aqueous secondary battery, for example, Patent Document 2 proposes to coat a positive electrode active material with a silane compound.